High pressure compressor seal-ring with improved wear resistance

ABSTRACT

A compressor seal-ring assembly includes a seal formed of a nickel, cobalt or iron-based superalloy; a counterface positioned for sealing interaction with the seal; and a lubricant coating on the seal, the lubricant coating being formed of a CoCrAlY-containing material.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 16/269,673, filed Feb. 7, 2019.

BACKGROUND

The present disclosure relates to a compressor seal-ring assembly and,more particularly, to a high-pressure compressor seal-ring assembly witha coating system to improve wear resistance.

Gas turbine engines typically include compressors having multiple rows,or stages, of rotating blades and multiple stages of stators. In someparts of the gas turbine engine, it is desirable to create a sealbetween two volumes. For example, a first volume can define a portion ofthe gas path which receives relatively hot fluid. Fluid within a secondvolume can be used to cool components of the gas turbine engine and,thus, have a lower temperature than the fluid within the first volume. Aseal can be used to seal the first volume from the second volume as someparts defining the first and/or second volume move and/or rotate withrespect to other parts defining the first and/or second volume.

One specific location of a seal in such an engine is between componentsof a high-pressure compressor, for example between a rotor such as anintegrated blade rotor (IBR) and a shaft on which the IBR is positioned.

In some high pressure compressor piston-seals, operation is carried outat elevated temperatures and conditions of high vibratory motion.Existing seal rings are typically manufactured from, or provided havingouter surfaces of, a nickel superalloy such as IN718, which cantypically be coated with a copper aluminum alloy. The correspondingsurface of the IBR is typically fabricated from a nickel basedsuperalloy such as DA718. Due to poor tribological behavior of thesealloys in combination with the high temperature exposure and highvibratory energy in the system, these materials are not capable ofeffectively operating under the harsh conditions, continuously resultingin premature failure of the seal due to wear issues.

In addition to the need to constantly replace such seals after excessivewear, this situation can also frequently cause costly damage to otherparts, such as to the counterface of the IBR, which is a critical andexpensive part.

The present disclosure is directed to addressing this issue.

SUMMARY OF THE INVENTION

A compressor seal-ring assembly according to one embodiment of thepresent disclosure comprises a seal comprising a nickel, cobalt oriron-based superalloy; a counterface positioned for sealing interactionwith the seal; and a lubricant coating on the seal, the lubricantcoating comprising a CoCrAlY-containing material.

In one non-limiting embodiment, the lubricant coating has a thickness ofbetween 0.001 and 0.006 inches.

In another non-limiting embodiment, the lubricant coating has athickness of between 0.003 and 0.005 inches.

In a further non-limiting embodiment, the lubricant coating comprisesbetween 75 and 98% wt. of CoCrAlY and between 2 and 25% wt. of hBN.

In still another non-limiting embodiment, the assembly further comprisesan additional lubricant coating on the counterface.

In a still further non-limiting embodiment, the additional lubricantcoating comprises hBN.

In another non-limiting embodiment, the additional lubricant coating hasa thickness of between 0.0001 and 0.002 inches.

In a further non-limiting embodiment, the additional lubricant coatinghas a thickness of between 0.0005 and 0.001 inches.

In another non-limiting embodiment, the additional lubricant coating isa solid lubricant paste.

In still another non-limiting embodiment, the solid lubricant pastecontains <10% wt. of binder constituents.

In another non-limiting embodiment, the counterface is a surface of arotor, and the seal is mounted between the rotor and an outer shaft onwhich the rotor is mounted.

In a further non-limiting embodiment, the rotor is a component of a highpressure compressor of a gas turbine engine.

In a non-limiting embodiment, a method for improving wear resistance ofa compressor seal-ring assembly comprises positioning a seal comprisinga nickel, cobalt or iron-based superalloy for sealing interaction with acounterface, wherein the seal has a lubricant coating comprising aCoCrAlY material; and moving the counterface relative to the seal todeposit a transfer coating from the lubricant coating on thecounterface.

In another non-limiting embodiment, the transfer coating creates a Co—Cointerface between the seal and the counterface.

In a further non-limiting embodiment, the counterface is a surface of arotor.

In still another non-limiting embodiment, the method further comprisesapplying an additional lubricant coating to the counterface.

In a still further non-limiting embodiment, the additional lubricantcoating comprises hBN.

In another non-limiting embodiment, the additional lubricant coating isapplied as a solid lubricant paste, and the method further comprisescuring the solid lubricant paste to produce the additional lubricantcoating.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A detailed description of preferred embodiments of the presentdisclosure follows, with referenced to the attached drawings, wherein:

FIG. 1 illustrates a portion of a gas turbine engine showing theenvironment surrounding a seal assembly of the present disclosure;

FIG. 2 is an enlarged portion of FIG. 1 showing a non-limitingembodiment of the disclosed seal assembly;

FIGS. 3A and B show cross-sections taken through a seal and counterfaceof a compressor seal-ring assembly according to two differentembodiments of the present disclosure; and

FIG. 4 illustrates the wear results of the presently disclosed system ascompared to a prior art system as discussed above.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

The disclosure relates to a compressor seal-ring assembly and moreparticularly to a coating system for use with a seal ring and associatedrotor such as an integrated blade rotor (IBR).

FIG. 1 shows high pressure compressor 10 which includes a plurality ofintegrally bladed rotors (IBR) including IBRs 12, 14, 16. IBR 12includes a rotor disk portion 18 and a blade portion 20. Rotor diskportion 18 and blade portion 20 are portions of a single component.Similar components are present in the other IBRs as well.

High pressure compressor 10 includes a hub rotor 22 having a radiallyinner arm 24 coupled to outer shaft 26 via an engine nut 28. A seal ring30 is positioned between an outer arm 32 of hub rotor 22 and a portionof rotor disk portion 18 of IBR 12. A rotor stack 34 (including IBRs 12,14 and 16 as well as other IBRs of high pressure compressor 10) of highpressure compressor 10 is coupled to outer shaft 26 at a locationforward of IBR 16. In that regard, rotor stack 34 and seal ring 30 areheld in place via compressive force applied via the coupling of rotorstack 34 to outer shaft 26 at the forward location and via the couplingof hub rotor 22 to outer shaft 26. Compressive force is defined as aforce applied to an object from two sides that does not necessarilycause the object to reduce in size, quantity or volume. Stateddifferently, seal ring 30 is held in place by compressive force appliedto seal ring 30 as a result of a forward force applied by hub rotor 22and an aftward force applied by IBR 12. In that regard, seal ring 30 canbe press fit into place between outer arm 32 of hub rotor 22 and rotordisk portion 18 of IBR 12.

IBR 16 is shown sealed against outer shaft 26 at the portion circled atA, which is enlarged in FIG. 2 .

FIG. 2 shows IBR 16, and specifically a counterface 36 of IBR 16, aswell as a portion of outer shaft 26 against which a seal is needed. Asshown, a radially outwardly facing groove 38 can be defined on outershaft 26, and a seal 40 can be disposed in groove 38 for sealing againstcounterface 36. In this location, seal 40 is considered a high pressurecompressor piston-seal. Lubrication of the interface between seal 40 andcounterface 36 is the focus of the present disclosure.

FIG. 3 is an enlarged view of the interface between seal 40 andcounterface 36. At this location, a high energy vibratory motion isencountered by the seal and counterface, which is schematicallyrepresented by arrow B. This vibratory motion, especially at theelevated temperatures to which this area is subjected, namely betweenabout 350 and 900° F., can lead to rapid failure or at least wear ofseal 40, which can in turn lead to damage to counterface 36 of the IBR,which leads to costly overhaul.

In high detail photography of a conventional seal and corresponding IBRsurface after a certain amount of operation of these components at hightemperatures and high conditions of vibratory energy, the surface of theseal is worn and damaged, and a corresponding portion of the surface ofthe IBR is also visibly pitted and worn in a manner which can requireexpensive and time-consuming repair and/or replacement. The lubricantsystem disclosed herein addresses this problem.

Seal 40 is typically a ring seal which can be fabricated from a nickel,cobalt or iron superalloy. Specific non-limiting examples of suitablematerial include IN 718 nickel superalloy, Haynes 25 cobalt alloy andA286 iron based superalloy, and numerous other examples of othersuitable materials would be well known to a person having ordinary skillin the art.

The counterface 36 of IBR 16 can typically be fabricated from a nickelbased superalloy such as DA718. This material would typically be thematerial from which at least this portion of the IBR is fabricated.

In conventional seals, a coating is produced on the seal, wherein theconventional coating is a copper aluminum alloy. This coating has beenfound to be insufficient, and results in the unacceptable wear discussedabove. Therefore, as disclosed herein, a coating 42 (FIG. 3 ) can beapplied to seal 40, wherein the coating 42 is a lubricant coating thatreduces friction and wear between seal 40 and counterface 36 due toexcessive heat and vibratory movement or fretting. This lubricantcoating, in the disclosed embodiment, is applied to an outer radius ofthe ring shaped seal so as to be positioned for sealing interaction withcounterface 36.

Lubricant coating 42 is advantageously provided from a CoCrAlY alloy,which can advantageously be blended with hBN. A specific example of asuitable blend of these materials is AMDRY-958 provided by OerlikonMetco which is a particularly well-suited lubricant coating for use inthe seal system of the present disclosure. The lubricant coating in thisnon-limiting embodiment can by provided as a mixture of between about 75and 98% wt. CoCrAlY and between about 2 and 25% wt. hBN, although otherratios of components can also be utilized. One particularly suitableblend is 85% wt. CoCrAlY and 15% wt. hBN. Further, lubricant coating 42advantageously has a thickness of between about 0.001 and about 0.006inches, preferably between about, more preferably between 0.003 and0.005 inches.

Lubricant coating 42 can advantageously be produced on seal 40 innumerous different ways, but one particularly well suited butnon-limiting example of application method is through plasma spray.

In a further non-limiting embodiment, counterface 36 can also beprovided with an additional lubricant coating 44. Additional lubricantcoating 44 can be hBN or an hBN-based solid lubricant paste, which canbe applied to counterface 36. This additional lubricant coating helps tofurther reduce friction between counterface 36 and seal 40. The solidlubricant may suitably contain less than about 10% wt. of binderconstituents. This coating can have a thickness of between about 0.0001and about 0.002, preferably between 0.0005 and 0.001 inches.

The additional lubricant coating can be applied to IBR counterface 36 bybrushing or swabbing, as non-limiting examples. Alternatively, theadditional lubricant coating can be applied by spraying, or othersuitable methods. When applied as a solid lubricant paste, the paste canthen suitable be cured at elevated temperature to produce the desiredadditional lubricant coating.

Lubricant coating 42 alone produces an improved sliding regime betweenthe seal ring 40 and counterface 36 as compared to the conventionalstructures mentioned above. This serves to reduce overall wear of theinterface between the seal and counterface. Further, adding additionallubricant coating 44 to counterface 36 of the IBR even further reducesoverall wear at the interface, and thereby can greatly reduce the costand frequency of repair and overhaul of these components.

Additional lubricant coating 44 can also reduce the breaking-in periodbetween the surfaces. More specifically, upon initial motion, basalplanes of the additional lubricant coating (hBN) become parallel to thesliding direction, thereby reducing the coefficient of friction.

Wear volume was measured for a prior art coating system having a copperaluminum alloy coating on the seal, and also for a coating system of thepresent disclosure including an 85%/15% lubricant coating of CoCrAlY andhBN as discussed above, applied to the seal with no additional coatingon the IBR. These tests were conducted on a custom build rig with apin-on-flat configuration. FIG. 4 shows the results of this testing interms of normalized wear volume for piston seal coating and counterfaceof the IBR. In FIG. 4 , data on the left side of the drawing shows wearof the piston seal-coating at 50, and wear of the counterface of the IBRat 52. As shown, there was considerable wear to the IBR. On the rightside of the drawing, wear on the piston seal-coating of the inventivecoating system is shown at 54, and there was no measurable wear to theIBR counterface.

In the left side of FIG. 4 , using conventional seal and coating,significant wear volume is shown, for both components. In the right-sideportion of FIG. 4 , it can be seen that the wear volume is slightlyhigher on the piston seal/coating side, but is virtually eliminated onthe counterface side. The slight increase in piston seal-coating wear isaccounted for by creation of a transfer coating 45 (See FIGS. 3A and 3B)on the counterface surface of the IBR. This is desirable, as thetransfer coating consists of cobalt from the CoCrAlY lubricant coatingwhich is positioned on the seal, and this transfer coating creates acobalt-cobalt sliding regime between the seal and counterface. Thissliding regime is subject to extremely low friction and greatly reducesor eliminates wear problems due to the high vibratory energy encounteredin this interface, as well as the high temperatures. Thus, the lubricantsystem of the present disclosure greatly reduces or eliminates wear tothe expensive IBR component.

It should be noted that the testing conducted as represented in FIG. 4was conducted without utilizing the additional lubricant coating on thecounterface or IBR side as discussed above. With this optionaladditional lubricant coating, the wear can be even more greatly reduced.

Low friction and wear resistant piston seals or rings as disclosedherein are capable of operating efficiently in high pressure compressorstatic sealing applications and will significantly increase theendurance life of engine components. In addition, this technology maysignificantly reduce overhaul costs by reducing the number of parts (inparticular the more-expensive counterparts) that are stripped due towear and thermal damage issues (e.g. caused by frictional heating).

One or more embodiments of the present invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention. Forexample, the disclosed lubricant coatings can be applied at othersimilar locations within a gas turbine engine and produce benefits fromsuch application as well. Further, the coating materials disclosedherein and their equivalents can be utilized with components ofdifferent underlying materials, all within the broad scope of thedisclosure. Accordingly, other embodiments are within the scope of thefollowing claims.

What is claimed is:
 1. A compressor seal-ring assembly, comprising: aseal comprising a nickel, cobalt or iron-based superalloy; a counterfacepositioned for sealing interaction with the seal, wherein the seal andcounterface define a static seal; and a lubricant coating on the seal,the lubricant coating comprising a CoCrAlY-containing material.
 2. Theassembly of claim 1, wherein the lubricant coating has a thickness ofbetween 0.001 and 0.006 inches.
 3. The assembly of claim 1, wherein thelubricant coating has a thickness of between 0.003 and 0.005 inches. 4.The assembly of claim 1, wherein the lubricant coating comprises between75 and 98% wt. of CoCrAlY and between 2 and 25% wt. of hBN.
 5. Theassembly of claim 4, wherein the additional lubricant coating is a solidlubricant paste.
 6. The assembly of claim 5, wherein the solid lubricantpaste contains <10% wt. of binder constituents.
 7. The assembly of claim1, further comprising an additional lubricant coating on thecounterface.
 8. The assembly of claim 7, wherein the additionallubricant coating comprises hBN.
 9. The assembly of claim 7, wherein theadditional lubricant coating has a thickness of between 0.0001 and 0.002inches.
 10. The assembly of claim 7, wherein the additional lubricantcoating has a thickness of between 0.0005 and 0.001 inches.
 11. Theassembly of claim 1, wherein the counterface is a surface of a rotor,and the seal is mounted between the rotor and an outer shaft on whichthe rotor is mounted.
 12. The assembly of claim 11, wherein the rotor isa component of a high pressure compressor of a gas turbine engine. 13.The assembly of claim 1, wherein the lubricant coating comprises CoCrAlYand hBn.
 14. A method for improving wear resistance of a compressorseal-ring assembly, comprising: positioning a seal comprising a nickel,cobalt or iron-based superalloy for sealing interaction with acounterface, wherein the seal and the counterface define a static sealand wherein the seal has a lubricant coating comprising a CoCrAlYmaterial; and moving the counterface relative to the seal to deposit atransfer coating from the lubricant coating on the counterface, whereinthe moving comprises a vibratory motion of the seal relative to thecounterface.
 15. The method of claim 14, wherein the transfer coatingcreates a Co—Co interface between the seal and the counterface.
 16. Themethod of claim 14, wherein the counterface is a surface of a rotor. 17.The method of claim 14, further comprising the step of applying anadditional lubricant coating to the counterface.
 18. The method of claim17, wherein the additional lubricant coating comprises hBN.
 19. Themethod of claim 17, wherein the additional lubricant coating is appliedas a solid lubricant paste, and further comprising curing the solidlubricant paste to produce the additional lubricant coating.
 20. Themethod of claim 14, wherein the lubricant coating comprises CoCrAlY andhBn.